1. Field of the Invention
The present invention relates to a worm type reduction gear mechanism which is improved over a worm reduction gear mechanism to be used in case a high reduction gear ratio is required for all industrial fields.
2. Description of the Related Art
The worm reduction gear mechanism widely used and well known in the art is a rotation transmitting means which has two staggered shafts. In this mechanism, one gear consists of a worm having one to four threads (or teeth), and the other gear consists of a worm wheel which has a number of teeth meshing with the teeth of the worm.
This worm reduction gear mechanism is advantageous in that a relatively high reduction ratio can be achieved at a low cost and in a small size. The contacting portions of the worm and the worm wheel frictionally interact so that the transmission efficiency is lower than those of the remaining reduction gear mechanisms. A high reduction ratio produces many problems, such that the back-lash is so high as to severely reduce the transmission efficiency, and that the worm wheel has to be made of an expensive non-ferrous material because to reduce wear or the likelihood of seizure.